U.S. patent application number 13/983782 was filed with the patent office on 2013-11-28 for tempered glass plate.
This patent application is currently assigned to NIPPON ELECTRIC GLASS CO., LTD.. The applicant listed for this patent is Kosuke Kawamoto, Takashi Murata. Invention is credited to Kosuke Kawamoto, Takashi Murata.
Application Number | 20130316162 13/983782 |
Document ID | / |
Family ID | 46638630 |
Filed Date | 2013-11-28 |
United States Patent
Application |
20130316162 |
Kind Code |
A1 |
Murata; Takashi ; et
al. |
November 28, 2013 |
TEMPERED GLASS PLATE
Abstract
Provided is a tempered glass sheet having a compression stress
layer in a surface thereof, comprising, as a glass composition
expressed in mass % in terms of oxides, 50 to 70% of SiO.sub.2, 5
to 20% of Al.sub.2O.sub.3, 0 to 5% of B.sub.2O.sub.3, 8 to 18% of
Na.sub.2O, 2 to 9% of K.sub.2O, and 30 to 1,500 ppm of
Fe.sub.2O.sub.3, and having a spectral transmittance in terms of a
thickness of 1.0 mm at a wavelength of 400 to 700 nm of 85% or
more, a chromaticity x of 0.3095 to 0.3120 in xy chromaticity
coordinates (illuminant C, in terms of a thickness of 1 mm), and a
chromaticity y of 0.3160 to 0.3180 in xy chromaticity coordinates
(illuminant C, in terms of a thickness of 1 mm).
Inventors: |
Murata; Takashi; (Shiga,
JP) ; Kawamoto; Kosuke; (Shiga, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Murata; Takashi
Kawamoto; Kosuke |
Shiga
Shiga |
|
JP
JP |
|
|
Assignee: |
NIPPON ELECTRIC GLASS CO.,
LTD.
Otsu-shi, Shiga
JP
|
Family ID: |
46638630 |
Appl. No.: |
13/983782 |
Filed: |
February 7, 2012 |
PCT Filed: |
February 7, 2012 |
PCT NO: |
PCT/JP2012/052714 |
371 Date: |
August 6, 2013 |
Current U.S.
Class: |
428/220 ;
428/410; 501/66; 501/68 |
Current CPC
Class: |
C03C 3/087 20130101;
C03C 3/11 20130101; C03C 3/093 20130101; Y10T 428/315 20150115 |
Class at
Publication: |
428/220 ;
428/410; 501/66; 501/68 |
International
Class: |
C03C 3/093 20060101
C03C003/093; C03C 3/087 20060101 C03C003/087 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 10, 2011 |
JP |
2011-026661 |
Claims
1. A tempered glass sheet having a compression stress layer in a
surface thereof, comprising, as a glass composition expressed in
mass % in terms of oxides, 50 to 70% of SiO.sub.2, 5 to 20% of
Al.sub.2O.sub.3, 0 to 5% of B.sub.2O.sub.3, 8 to 18% of Na.sub.2O,
2 to 9% of K.sub.2O, and 30 to 1,500 ppm of Fe.sub.2O.sub.3, and
having a spectral transmittance in terms of a thickness of 1.0 mm
at a wavelength of 400 to 700 nm of 85% or more, a chromaticity x
of 0.3095 to 0.3120 in xy chromaticity coordinates (illuminant C,
in terms of a thickness of 1 mm), and a chromaticity y of 0.3160 to
0.3180 in xy chromaticity coordinates (illuminant C, in terms of a
thickness of 1 mm).
2. The tempered glass sheet according to claim 1, wherein a
compression stress value of the compression stress layer is 400 MPa
or more, and a depth of the compression stress layer is 30 .mu.m or
more.
3. The tempered glass sheet according to claim 1, further
comprising 0 to 50,000 ppm of TiO.sub.2.
4. The tempered glass sheet according to claim 1, further
comprising 50 to 30,000 ppm of SnO.sub.2+SO.sub.3+Cl.
5. The tempered glass sheet according to claim 1, further
comprising 0 to 10,000 ppm of CeO.sub.2 and 0 to 10,000 ppm of
WO.sub.3.
6. The tempered glass sheet according to claim 1, further
comprising 0 to 500 ppm of NiO.
7. The tempered glass sheet according to claim 1, wherein the
tempered glass sheet has a thickness of 0.5 to 2.0 mm.
8. The tempered glass sheet according to claim 1, wherein the
tempered glass sheet has a temperature at 10.sup.2.5 dPas of
1,600.degree. C. or less.
9. The tempered glass sheet according to claim 1, wherein the
tempered glass sheet has a liquidus temperature of 1,100.degree. C.
or less.
10. The tempered glass sheet according to claim 1, wherein the
tempered glass sheet has a liquidus viscosity of 10.sup.4.0 dPas or
more.
11. The tempered glass sheet according to claim 1, wherein the
tempered glass sheet has a density of 2.6 g/cm.sup.3 or less.
12. The tempered glass sheet according to claim 1, wherein the
tempered glass sheet has a thermal expansion coefficient of 85 to
110.times.10.sup.-7/.degree. C. in a temperature range of from 30
to 380.degree. C.
13. The tempered glass sheet according to claim 1, wherein the
tempered glass sheet has a .beta.-OH value of 0.25 mm.sup.-1 or
less.
14. The tempered glass sheet according to claim 1, wherein the
tempered glass sheet is used for a protective member for a touch
panel display.
15. The tempered glass sheet according to claim 1, wherein the
tempered glass sheet is used for a cover glass for a cellular
phone.
16. The tempered glass sheet according to claim 1, wherein the
tempered glass sheet is used for a cover glass for a solar
cell.
17. The tempered glass sheet according to claim 1, wherein the
tempered glass sheet is used for a protective member for a
display.
18. The tempered glass sheet according to claim 1, wherein the
tempered glass sheet is used for an exterior component having such
a form that a part or whole of an end surface of the tempered glass
sheet is exposed to an outside.
19. A tempered glass sheet having a compression stress layer in a
surface thereof, comprising, as a glass composition expressed in
mass % in terms of oxides, 50 to 70% of SiO.sub.2, 12 to 18% of
Al.sub.2O.sub.3, 0 to 1% of B.sub.2O.sub.3, 12 to 16% of Na.sub.2O,
3 to 7% of K.sub.2O, 100 to 300 ppm of Fe.sub.2O.sub.3, 0 to 5,000
ppm of TiO.sub.2, and 50 to 9,000 ppm of SnO.sub.2+SO.sub.3+Cl, and
having a compression stress value of the compression stress layer
of 600 MPa or more, a depth of the compression stress layer of 50
.mu.m or more, a liquidus viscosity of 10.sup.5.5 dPas or more, a
.beta.-OH value of 0.25 mm.sup.-1 or less, a spectral transmittance
in terms of a thickness of 1.0 mm at a wavelength of 400 to 700 nm
of 87% or more, a chromaticity x of 0.3095 to 0.3110 in xy
chromaticity coordinates (illuminant C, in terms of a thickness of
1 mm), and a chromaticity y of 0.3160 to 0.3170 in xy chromaticity
coordinates (illuminant C, in terms of a thickness of 1 mm).
20. A glass sheet to be tempered, comprising, as a glass
composition expressed in mass % in terms of oxides, 50 to 70% of
SiO.sub.2, 5 to 20% of Al.sub.2O.sub.3, 0 to 5% of B.sub.2O.sub.3,
8 to 18% of Na.sub.2O, 2 to 9% of K.sub.2O, and 30 to 1,500 ppm of
Fe.sub.2O.sub.3, and having a spectral transmittance in terms of a
thickness of 1.0 mm at a wavelength of 400 to 700 nm of 85% or
more, a chromaticity x of 0.3095 to 0.3120 in xy chromaticity
coordinates (illuminant C, in terms of a thickness of 1 mm), and a
chromaticity y of 0.3160 to 0.3180 in xy chromaticity coordinates
(illuminant C, in terms of a thickness of 1 mm).
Description
TECHNICAL FIELD
[0001] The present invention relates to a tempered glass sheet, and
more specifically, to a tempered glass sheet suitable for a cover
glass for a cellular phone, a digital camera, a personal digital
assistant (PDA), or a solar cell, or a glass substrate for a
display, in particular, a touch panel display.
BACKGROUND ART
[0002] In recent years, a PDA equipped with a touch panel display
has been developed, and a tempered glass sheet has been used for
protecting a display part thereof. A market for the tempered glass
sheet is expected to grow bigger and bigger in the future (see, for
example, Patent Literature 1 and Non Patent Literature 1).
[0003] The tempered glass sheet for this application is required to
have a high mechanical strength.
CITATION LIST
Patent Literature
[0004] Patent Literature 1: JP 2006-83045 A
Non Patent Literature
[0004] [0005] Non Patent Literature 1: Tetsuro Izumitani et al.,
"New glass and physical properties thereof," First edition,
Management System Laboratory. Co., Ltd., Aug. 20, 1984, p.
451-498
SUMMARY OF INVENTION
Technical Problem
[0006] Hitherto, there has been employed such a form that, once an
end surface of a tempered glass sheet (cover glass) for protecting
a display is incorporated into a chassis of a device, a portion of
the end surface of the tempered glass sheet cannot be touched by
users. However, in recent years, such a form that the tempered
glass sheet is attached outside the device has been studied in
order to enhance designability. Thus, the end surface of the cover
glass has also been considered to be a part of a design.
[0007] When apart or the whole of the end surface of the tempered
glass sheet is exposed to the outside, it is necessary to take care
not to impair appearance of the device. In this case, a color of
the tempered glass sheet is important. Specifically, it is
important that the tempered glass sheet do not have a bluish or
yellowish color when the tempered glass sheet is seen from the end
surface side thereof.
[0008] Further, in order to enhance a mechanical strength of a
tempered glass, a compression stress value of its compression
stress layer needs to be increased. A component such as
Al.sub.2O.sub.3 is known as a component that is capable of
increasing the compression stress value. However, when the content
of Al.sub.2O.sub.3 is too large, there is a problem in that an
Al.sub.2O.sub.3 raw material is liable to remain unmelted at the
time of melting of glass, resulting in many glass defects. When
feldspar or the like is used as the Al.sub.2O.sub.2 raw material,
the problem can be solved. However, an increased content of
Fe.sub.2O.sub.3 in a glass composition due to Fe.sub.2O.sub.3
contained in the feldspar makes it difficult to adjust the color of
the glass to a desired one. Further, when a hydrate raw material is
used as well, the above-mentioned problem can be solved. However,
an increased content of water in the glass makes it difficult to
increase the compression stress value.
[0009] Thus, a technical object of the present invention is to
provide a tempered glass sheet comprising a compression stress
layer with a high compression stress value and having a desired
color.
Solution to Problem
[0010] The inventors of the present invention have made various
studies and have consequently found that the technical object
described above can be achieved by controlling the content of each
component in a glass composition and glass characteristics within
predetermined ranges. Thus, the finding is proposed as the present
invention. That is, a tempered glass sheet of the present invention
is a tempered glass sheet having a compression stress layer in a
surface thereof, comprising, as a glass composition expressed in
mass % in terms of oxides, 50 to 70% of SiO.sub.2, 5 to 20% of
Al.sub.2O.sub.2, 0 to 5% of B.sub.2O.sub.3, 8 to 18% of Na.sub.2O,
2 to 9% of K.sub.2O, and 30 to 1,500 ppm (0.003 to 0.15%) of
Fe.sub.2O.sub.3, and having a spectral transmittance in terms of a
thickness of 1.0 mm at a wavelength of 400 to 700 nm of 85% or
more, x in xy chromaticity coordinates (illuminant C, in terms of a
thickness of 1 mm) of 0.3095 to 0.3120, and y in xy chromaticity
coordinates (illuminant C, in terms of a thickness of 1 mm) of
0.3160 to 0.3180. Herein, the phrase "in terms of oxides" means
that, when Fe.sub.2O.sub.3 is taken as an example, not only iron
oxide present in the state of Fe.sup.3+ but also iron oxide present
in the state of Fe.sup.2+ are expressed as Fe.sub.2O.sub.3 after
being converted to Fe.sub.2O.sub.3 (the same holds true for other
oxides). The "spectral transmittance in terms of a thickness of 1.0
mm at a wavelength of 400 to 700 nm" can be measured, for example,
at a slit width of 2.0 nm at a medium scan speed at a sampling
pitch of 0.5 nm by using UV-3100 PC (manufactured by Shimadzu
Corporation). The "x in xy chromaticity coordinates (illuminant C,
in terms of a thickness of 1 mm)" can be measured by using, for
example, UV-3100 PC (manufactured by Shimadzu Corporation). The "y
in xy chromaticity coordinates (illuminant C, in terms of a
thickness of 1 mm)" can be measured by using, for example, UV-3100
PC (manufactured by Shimadzu Corporation).
[0011] Second, in the tempered glass sheet of the present
invention, it is preferred that the compression stress value of the
compression stress layer be 400 MPa or more, and the depth
(thickness) of the compression stress layer be 30 .mu.m or more.
Herein, the term "compression stress value of the compression
stress layer" and the term "depth of the compression stress layer"
refer to values which are calculated from the number of
interference fringes on a sample and each interval between the
interference fringes, the interference fringes being observed when
a surface stress meter (such as FSM-6000 manufactured by Toshiba
Corporation) is used to observe the sample.
[0012] Third, the tempered glass sheet of the present invention
preferably further comprises 0 to 50,000 ppm of TiO.sub.2.
[0013] Fourth, the tempered glass sheet of the present invention
preferably further comprises 50 to 30,000 ppm of
SnO.sub.2+SO.sub.3+Cl. Herein, the term "SnO.sub.2+SO.sub.3+Cl"
refers to the total amount of SnO.sub.2, SO.sub.3, and Cl.
[0014] Fifth, the tempered glass sheet of the present invention
preferably further comprises 0 to 10,000 ppm of CeO.sub.2 and 0 to
10,000 ppm of WO.sub.3.
[0015] Sixth, the tempered glass sheet of the present invention
preferably further comprises 0 to 500 ppm of NiO.
[0016] Seventh, the tempered glass sheet of the present invention
preferably has a thickness of 0.5 to 2.0 mm.
[0017] Eighth, the tempered glass sheet of the present invention
preferably has a temperature at 10.sup.2.5 dPas of 1,600.degree. C.
or less. Herein, the term "temperature at 10.sup.2.5 dPas" refers
to a value obtained by measurement using a platinum sphere pull up
method.
[0018] Ninth, the tempered glass sheet of the present invention
preferably has a liquidus temperature of 1,100.degree. C. or less.
Herein, the term "liquidus temperature" refers to a temperature at
which crystals of glass deposit after glass powder that has passed
through a standard 30-mesh sieve (sieve opening: 500 .mu.m) and
remained on a 50-mesh sieve (sieve opening: 300 .mu.m) is placed in
a platinum boat and then kept in a gradient heating furnace for 24
hours.
[0019] Tenth, the tempered glass sheet of the present invention
preferably has a liquidus viscosity of 10.sup.4.0 dPas or more.
Herein, the term "liquidus viscosity" refers to a value obtained by
measurement of the viscosity of glass at the liquidus temperature
using a platinum sphere pull up method.
[0020] Eleventh, the tempered glass sheet of the present invention
preferably has a density of 2.6 g/cm.sup.3 or less. Herein, the
"density" may be measured by a well-known Archimedes method.
[0021] Twelfth, the tempered glass sheet of the present invention
preferably has a thermal expansion coefficient in the temperature
range of 30 to 380.degree. C. of 85 to 110.times.10.sup.-7/.degree.
C. Herein, the term "thermal expansion coefficient in the
temperature range of 30 to 380.degree. C." refers to a value
obtained by measurement of an average thermal expansion coefficient
with a dilatometer.
[0022] Thirteenth, the tempered glass sheet of the present
invention preferably has a .beta.-OH value of 0.25 mm.sup.-1 or
less. Herein, the term ".beta.-OH value" refers to a value
calculated from the following equation by measuring the
transmittance of the glass by FT-IR.
.beta.-OH value=(1/X)log.sub.10(T.sub.1/T.sub.2)
[0023] X: thickness (mm)
[0024] T.sub.1: transmittance (%) at a reference wavelength of
3,846 cm.sup.-1
[0025] T.sub.2: minimum transmittance (%) at a hydroxyl group
absorption wavelength of around 3,600 cm.sup.-1
[0026] Fourteenth, the tempered glass sheet of the present
invention is preferably used for a protective member for a touch
panel display.
[0027] Fifteenth, the tempered glass sheet of the present invention
is preferably used for a cover glass for a cellular phone.
[0028] Sixteenth, the tempered glass sheet of the present invention
is preferably used for a cover glass for a solar cell.
[0029] Seventeenth, the tempered glass sheet of the present
invention is preferably used for a protective member for a
display.
[0030] Eighteenth, the tempered glass sheet of the present
invention is preferably used for an exterior component having such
a form that a part or whole of the end surface of the tempered
glass sheet is exposed to the outside. Herein, when an end edge
region at which a surface and end surface of the tempered glass
sheet cross to each other is subjected to chamfering processing,
the "end surface" includes the chamfered surface of the end edge
region.
[0031] Nineteenth, a tempered glass sheet of the present invention
is a tempered glass sheet having a compression stress layer in a
surface thereof, comprising, as a glass composition expressed in
mass % in terms of oxides, 50 to 70% of SiO.sub.2, 12 to 18% of
Al.sub.2O.sub.3, 0 to 1% of B.sub.2O.sub.3, 12 to 16% of Na.sub.2O,
3 to 7% of K.sub.2O, 100 to 300 ppm of Fe.sub.2O.sub.3, 0 to 5,000
ppm of TiO.sub.2, and 50 to 9,000 ppm of SnO.sub.2+SO.sub.3+Cl, and
having a compression stress value of the compression stress layer
of 600 MPa or more, a depth of the compression stress layer of 50
.mu.m or more, a liquidus viscosity of 10.sup.5.5 dPas or more, a
.beta.-OH value of 0.25 mm.sup.-1 or less, a spectral transmittance
in terms of a thickness of 1.0 mm at a wavelength of 400 to 700 nm
of 87% or more, x in xy chromaticity coordinates (illuminant C, in
terms of a thickness of 1 mm) of 0.3095 to 0.3110, and y in xy
chromaticity coordinates (illuminant C, in terms of a thickness of
1 mm) is 0.3160 to 0.3170.
[0032] Twentieth, a glass sheet to be tempered of the present
invention is a glass sheet to be tempered, comprising, as a glass
composition expressed in mass % in terms of oxides, 50 to 70% of
SiO.sub.2, 5 to 20% of Al.sub.2O.sub.3, 0 to 5% of B.sub.2O.sub.3,
8 to 18% of Na.sub.2O, 2 to 9% of K.sub.2O, and 30 to 1,500 ppm of
Fe.sub.2O.sub.3, and having a spectral transmittance in terms of a
thickness of 1.0 mm at a wavelength of 400 to 700 nm of 85% or
more, x in xy chromaticity coordinates (illuminant C, in terms of a
thickness of 1 mm) of 0.3095 to 0.3120, and y in xy chromaticity
coordinates (illuminant C, in terms of a thickness of 1 mm) of
0.3160 to 0.3180.
Advantageous Effects of Invention
[0033] According to the present invention, the content of each
component in the glass composition and the glass characteristics
are controlled within proper ranges, and hence the tempered glass
sheet comprising a compression stress layer with a high compression
stress value and having a desired color can be provided.
BRIEF DESCRIPTION OF DRAWING
[0034] FIG. 1 A schematic cross-sectional view for illustrating
Example 2 of the present invention, specifically, a schematic
cross-sectional view of a glass sheet to be tempered in its
thickness direction in the case where R processing has been applied
to the end edge regions of the glass sheet to be tempered.
DESCRIPTION OF EMBODIMENTS
[0035] A tempered glass sheet according to an embodiment of the
present invention has a compression stress layer in a surface
thereof. A method of forming a compression stress layer in a
surface of glass includes a physical tempering method and a
chemical tempering method. The tempered glass sheet according to
this embodiment is preferably produced by the chemical tempering
method.
[0036] The chemical tempering method is a method comprising
introducing alkali ions each having a large ion radius into a
surface of glass by ion exchange treatment at a temperature equal
to or lower than the strain point of the glass. When the chemical
tempering method is used to form a compression stress layer, the
compression stress layer can be properly formed even in the case
where a glass sheet to be tempered has a small thickness. In
addition, even when the compression stress layer is formed and then
the resultant tempered glass sheet is cut, the tempered glass sheet
does not easily break unlike a tempered glass sheet produced by
applying a physical tempering method such as an air cooling
tempering method.
[0037] Further, the tempered glass sheet according to this
embodiment comprises, as a glass composition expressed in mass % in
terms of oxides, 50 to 75% of SiO.sub.2, 5 to 20% of
Al.sub.2O.sub.3, 0 to 5% of B.sub.2O.sub.3, 8 to 18% of Na.sub.2O,
2 to 9% of K.sub.2O, and 30 to 1,500 ppm of Fe.sub.2O.sub.3. The
reason why the content range of each component is limited as
described above is shown below. Note that, in the description of
the content range of each component, the expression "%" means "mass
%."
[0038] SiO.sub.2 is a component that forms a network of glass. The
content of SiO.sub.2 is 50 to 70%, preferably 52 to 68%, 55 to 68%,
55 to 65%, particularly preferably 55 to 63%. When the content of
SiO.sub.2 is too small, vitrification does not occur easily, the
thermal expansion coefficient increases excessively, and the
thermal shock resistance is liable to lower. On the other hand,
when the content of SiO.sub.2 is too large, the meltability and
formability are liable to lower, and the thermal expansion
coefficient lowers excessively, with the result that it is
difficult to match the thermal expansion coefficient with those of
peripheral materials.
[0039] Al.sub.2O.sub.3 is a component that increases the ion
exchange performance and is a component that increases the strain
point or Young's modulus. The content of Al.sub.2O.sub.3 is 5 to
20%. When the content of Al.sub.2O.sub.3 is too small, the ion
exchange performance may not be exerted sufficiently. Thus, the
lower limit range of Al.sub.2O.sub.3 is suitably 7% or more, 8% or
more, 10% or more, particularly suitably 12% or more. On the other
hand, when the content of Al.sub.2O.sub.3 is too large, devitrified
crystals are liable to deposit in the glass, and it is difficult to
form a glass sheet by an overflow down-draw method, a float method,
or the like. Further, the thermal expansion coefficient lowers
excessively, and it is difficult to match the thermal expansion
coefficient with those of peripheral materials. In addition, the
viscosity at high temperature increases and the meltability is
liable to lower. Thus, the upper limit range of Al.sub.2O.sub.3 is
suitably 18% or less, 17% or less, particularly suitably 16% or
less.
[0040] B.sub.2O.sub.3 is a component that reduces the viscosity at
high temperature and density, stabilizes glass for crystals to be
unlikely precipitated, and reduces the liquidus temperature.
However, when the content of B.sub.2O.sub.3 is too large, through
ion exchange, coloring on a surface of glass called weathering
occurs, water resistance lowers, the compression stress value of
the compression stress layer lowers, and the depth of the
compression stress layer tends to lower. Thus, the content of
B.sub.2O.sub.3 is 0 to 5%, preferably 0 to 3%, 0 to 2%, 0 to 1.5%,
0 to 0.9%, 0 to 0.5%, particularly preferably 0 to 0.1%.
[0041] Na.sub.2O is an ion exchange component and is a component
that reduces the viscosity at high temperature to increase the
meltability and formability. Na.sub.2O is also a component that
improves the denitrification resistance. The content of Na.sub.2O
is 8 to 18%. When the content of Na.sub.2O is too small, the
meltability lowers, the thermal expansion coefficient lowers, and
the ion exchange performance is liable to lower. Thus, when
Na.sub.2O is added, the lower limit range of Na.sub.2O is suitably
10% or more, 11% or more, particularly suitably 12% or more. On the
other hand, when the content of Na.sub.2O is too large, the thermal
expansion coefficient becomes too large, the thermal shock
resistance lowers, and it is difficult to match the thermal
expansion coefficient with those of peripheral materials. Further,
the strain point lowers excessively, and the glass composition
loses its component balance, with the result that the
devitrification resistance lowers to the worse in some cases. Thus,
the upper limit range of Na.sub.2O is suitably 17% or less,
particularly suitably 16% or less.
[0042] K.sub.2O is a component that promotes ion exchange and is a
component that has a great effect of increasing the depth of the
compression stress layer among alkali metal oxides. K.sub.2O is
also a component that reduces the viscosity at high temperature to
increase the meltability and formability. K.sub.2O is also a
component that improves the devitrification resistance. The content
of K.sub.2O is 2 to 9%. When the content of K.sub.2O is too small,
it is difficult to obtain the above-mentioned effects. The lower
limit range of K.sub.2O is suitably 2.5% or more, 3% or more, 3.5%
or more, particularly suitably 4% or more. On the other hand, when
the content of K.sub.2O is too large, the thermal expansion
coefficient becomes too large, the thermal shock resistance lowers,
and it is difficult to match the thermal expansion coefficient with
those of peripheral materials. Further, the strain point lowers
excessively, and the glass composition loses its component balance,
with the result that the denitrification resistance tends to lower
to the worse. Thus, the upper limit range of K.sub.2O is suitably
8% or less, 7% or less, 6% or less, particularly suitably 5% or
less.
[0043] When a tempered glass is used for an exterior component or
the like having such a form that a part or the whole of the end
surface of the tempered glass is exposed to the outside, it is
important to regulate the content of Fe.sub.2O.sub.3 to 30 to 1,500
ppm, thereby controlling the color of the tempered glass. When the
content of Fe.sub.2O.sub.3 is too small, a high-purity glass raw
material needs to be used, with the result that the production cost
of the tempered glass significantly increases. The lower limit
range of Fe.sub.2O.sub.3 is suitably 0.005% or more, 0.008% or
more, particularly suitably 0.01% or more. On the other hand, when
the content of Fe.sub.2O.sub.3 is too large, the tempered glass is
liable to be colored. The upper limit range of Fe.sub.2O.sub.3 is
suitably 0.1% or less, 0.05% or less, particularly suitably 0.03%
or less. Note that the content of Fe.sub.2O.sub.3 in a conventional
tempered glass sheet is usually more than 1,500 ppm.
[0044] In addition to the above-mentioned components, for example,
the following components may be added.
[0045] Li.sub.2O is an ion exchange component and is a component
that reduces the viscosity at high temperature to increase the
meltability and formability and increases the Young's modulus. In
addition, Li.sub.2O has a great effect of increasing the
compression stress value among alkali metal oxides. However, when
the content of Li.sub.2O becomes extremely large in a glass system
comprising 5% or more of Na.sub.2O, the compression stress value
tends to lower to the worse. Further, when the content of Li.sub.2O
is too large, the liquidus viscosity lowers, the glass is liable to
devitrify, and the thermal expansion coefficient increases
excessively, with the result that the thermal shock resistance
lowers and it is difficult to match the thermal expansion
coefficient with those of peripheral materials. In addition, the
viscosity at low temperature lowers excessively, and the stress
relaxation occurs easily, with the result that the compression
stress value lowers to the worse in some cases. Thus, the content
of Li.sub.2O is preferably 0 to 15%, 0 to 4%, 0 to 2%, 0 to 1%, 0
to 0.5%, 0 to 0.3%, particularly preferably 0 to 0.1%.
[0046] The content of Li.sub.2O+Na.sub.2O+K.sub.2O is suitably 5 to
25%, 10 to 22%, 15 to 22%, particularly suitably 17 to 22%. When
the content of Li.sub.2O+Na.sub.2O+K.sub.2O is too small, the ion
exchange performance and meltability are liable to lower. On the
other hand, when the content of Li.sub.2O+Na.sub.2O+K.sub.2O is too
large, the glass is liable to devitrify, and the thermal expansion
coefficient increases excessively, with the result that the thermal
shock resistance lowers and it is difficult to match the thermal
expansion coefficient with those of peripheral materials. In
addition, the strain point lowers excessively, with the result that
a high compression stress value is hardly achieved in some cases.
Moreover, the viscosity at around the liquidus temperature lowers,
with the result that a high liquidus viscosity is hardly ensured in
some cases. Note that the term "Li.sub.2O+Na.sub.2O+K.sub.2O"
refers to the total amount of Li.sub.2O, Na.sub.2O, and
K.sub.2O.
[0047] MgO is a component that reduces the viscosity at high
temperature to increase the meltability and formability and
increases the strain point and Young's modulus, and is a component
that has a great effect of increasing the ion exchange performance
among alkaline earth metal oxides. However, when the content of MgO
is too large, the density and thermal expansion coefficient
increase, and the glass is liable to devitrify. Thus, the upper
limit range of MgO is suitably 12% or less, 10% or less, 8% or
less, 5% or less, particularly suitably 4% or less. Note that, when
MgO is added to the glass composition, the lower limit range of MgO
is suitably 0.5% or more, 1% or more, particularly suitably 2% or
more.
[0048] CaO has great effects of reducing the viscosity at high
temperature to enhance the meltability and formability and
increasing the strain point and Young's modulus without causing any
reduction in denitrification resistance as compared to other
components. The content of CaO is preferably 0 to 10%. However,
when the content of CaO is too large, the density and thermal
expansion coefficient increase, and the glass composition loses its
component balance, with the results that the glass is liable to
devitrify and the ion exchange performance is liable to lower to
the worse. Thus, the content of CaO is suitably 0 to 5%, 0 to 3%,
particularly suitably 0 to 2.5%.
[0049] SrO is a component that reduces the viscosity at high
temperature to increase the meltability and formability and
increases the strain point and Young's modulus without causing any
reduction in devitrification resistance. When the content of SrO is
too large, the density and thermal expansion coefficient increase,
the ion exchange performance lowers, and the glass composition
loses its component balance, with the result that the glass is
liable to devitrify to the worse. The content range of SrO is
suitably 0 to 5%, 0 to 3%, 0 to 1%, particularly suitably 0 to
0.1%.
[0050] BaO is a component that reduces the viscosity at high
temperature to increase the meltability and formability and
increases the strain point and Young's modulus without causing any
reduction in devitrification resistance. When the content of BaO is
too large, the density and thermal expansion coefficient increase,
the ion exchange performance lowers, and the glass composition
loses its component balance, with the result that the glass is
liable to devitrify to the worse. The content range of BaO is
suitably 0 to 5%, 0 to 3%, 0 to 1%, particularly suitably 0 to
0.1%.
[0051] ZnO is a component that increases the ion exchange
performance and is a component that has a great effect of
increasing the compression stress value, in particular. Further,
ZnO is a component that reduces the viscosity at high temperature
without reducing the viscosity at low temperature. However, when
the content of ZnO is too large, the glass manifests phase
separation, the devitrification resistance lowers, the density
increases, and the depth of the compression stress layer tends to
decrease. Thus, the content of ZnO is preferably 0 to 6%, 0 to 5%,
0 to 1%, particularly preferably 0 to 0.5%.
[0052] When a tempered glass is used for an exterior component or
the like having such a form that a part or the whole of the end
surface of the tempered glass is exposed to the outside, it is
preferred to regulate the content of TiO.sub.2, thereby controlling
the color of the tempered glass. TiO.sub.2 is a component that
enhances the ion exchange performance and is a component that
reduces the viscosity at high temperature. However, when the
content of TiO.sub.2 is too large, the glass is liable to be
colored and to denitrify. The upper limit range of TiO.sub.2 is
suitably 5% or less, 3% or less, 1% or less, 0.7% or less, 0.5% or
less, particularly suitably less than 0.5%. Note that, when
TiO.sub.2 is incorporated, the lower limit range of TiO.sub.2 is
suitably 0.001% or more, particularly suitably 0.005% or more.
[0053] WO.sub.3 is a component that is capable of controlling the
color of a tempered glass by causing color fading with the addition
of a color serving as a complementary color. Further, WO.sub.3 has
the property of suppressing denitrification resistance more from
deteriorating as compared to TiO.sub.2. On the other hand, when the
content of WO.sub.3 is too large, the tempered glass is liable to
be colored. The upper limit range of the content of WO.sub.3 is
suitably 5% or less, 3% or less, 2% or less, 1% or less,
particularly suitably 0.5% or less. Note that, when WO.sub.3 is
incorporated, the lower limit range of WO.sub.3 is suitably 0.001%
or more, particularly suitably 0.003% or more.
[0054] ZrO.sub.2 is a component that remarkably increases the ion
exchange performance and is a component that increases the
viscosity around the liquidus viscosity and the strain point.
However, when the content of ZrO.sub.2 is too large, the
denitrification resistance may lower remarkably and the density may
increase excessively. Thus, the upper limit range of ZrO.sub.2 is
suitably 10% or less, 8% or less, 6% or less, particularly suitably
5% or less. Note that, when the ion exchange performance is to be
increased, it is preferred to add ZrO.sub.2 to the glass
composition. In that case, the lower limit range of ZrO.sub.2 is
suitably 0.01% or more, 0.5% or more, 1% or more, 2% or more,
particularly suitably 4% or more.
[0055] P.sub.2O.sub.5 is a component that increases the ion
exchange performance and is a component that increases the depth of
the compression stress layer, in particular. However, when the
content of P.sub.2O.sub.5 is too large, the glass is liable to
manifest phase separation. Thus, the upper limit range of
P.sub.2O.sub.5 is suitably 10% or less, 8% or less, 6% or less,
particularly preferably 5% or less.
[0056] As a fining agent, one kind or two or more kinds selected
from the group consisting of As.sub.2O.sub.3, Sb.sub.2O.sub.3,
CeO.sub.2, SnO.sub.2, F, Cl, and SO.sub.3 (preferably the group
consisting of SnO.sub.2, Cl, and SO.sub.3) may be added at 0 to
30,000 ppm. The content of SnO.sub.2+SO.sub.3+Cl is preferably 0 to
1%, 50 to 5,000 ppm, 80 to 4,000 ppm, 100 to 3,000 ppm,
particularly preferably 300 to 3,000 ppm. Note that, when the
content of SnO.sub.2+SO.sub.3+Cl is less than 50 ppm, it is
difficult to obtain a fining effect. Herein, the term
"SnO.sub.2+SO.sub.3+Cl" refers to the total amount of SnO.sub.2,
SO.sub.3, and Cl.
[0057] The content range of SnO.sub.2 is suitably 0 to 10,000 ppm,
0 to 7,000 ppm, particularly suitably 50 to 6,000 ppm. The content
range of Cl is suitably 0 to 1,500 ppm, 0 to 1,200 ppm, 0 to 800
ppm, 0 to 500 ppm, particularly suitably 50 to 300 ppm. The content
range of SO.sub.3 is suitably 0 to 1,000 ppm, 0 to 800 ppm,
particularly suitably 10 to 500 ppm.
[0058] A transition metal element (such as Co or Ni) causing the
intense coloration of glass is a component that is capable of
controlling the color of a tempered glass by causing color fading
with the addition of a color serving as a complementary color. On
the other hand, the transition metal element may deteriorate the
transmittance of glass. In particular, when the glass is used for a
touch panel display, when the content of the transition metal
element is too large, the visibility of the touch panel display is
liable to lower. Thus, it is preferred to select a glass raw
material (including cullet) so that the content of a transition
metal oxide is 0.5% or less, 0.1% or less, particularly 0.05% or
less. Note that, when the transition metal element is incorporated,
the lower limit range of the transition metal element is suitably
0.0001% or more, particularly suitably 0.0003% or more.
[0059] A rare-earth oxide such as Nb.sub.2O.sub.5, La.sub.2O.sub.3,
or CeO.sub.2 is a component that increases the Young's modulus of
glass and is a component that is capable of controlling the color
of a tempered glass by causing color fading with the addition of a
color serving as a complementary color. However, the cost of the
raw material itself therefor is high. Further, when the rare-earth
oxide is added in a large amount, the denitrification resistance is
liable to deteriorate. Thus, the content of the rare-earth oxide is
preferably 4% or less, 3% or less, 2% or less, 1% or less, 0.5% or
less. Of those, CeO.sub.2 is a component that has a great color
fading action. The lower limit range of CeO.sub.2 is suitably 0.01%
or more, 0.03% or more, 0.05% or more, 0.1% or more, particularly
suitably 0.3% or more.
[0060] Further, the tempered glass sheet according to this
embodiment is preferably substantially free of As.sub.2O.sub.3,
Sb.sub.2O.sub.3, F, PbO, and Bi.sub.2O.sub.3 from environmental
considerations. Herein, the gist of the phrase "substantially free
of As.sub.2O.sub.3" resides in that As.sub.2O.sub.3 is not added
positively as a glass component, but contamination with
As.sub.2O.sub.3 as an impurity is allowable. Specifically, the
phrase means that the content of As.sub.2O.sub.3 is less than 500
ppm (by mass). The gist of the phrase "substantially free of
Sb.sub.2O.sub.3" resides in that Sb.sub.2O.sub.3 is not added
positively as a glass component, but contamination with
Sb.sub.2O.sub.3 as an impurity is allowable. Specifically, the
phrase means that the content of Sb.sub.2O.sub.3 is less than 500
ppm (by mass). The gist of the phrase "substantially free of F"
resides in that F is not added positively as a glass component, but
contamination with F as an impurity is allowable. Specifically, the
phrase means that the content of F is less than 500 ppm (by mass).
The gist of the phrase "substantially free of PbO" resides in that
PbO is not added positively as a glass component, but contamination
with PbO as an impurity is allowable. Specifically, the phrase
means that the content of PbO is less than 500 ppm (by mass). The
gist of the phrase "substantially free of Bi.sub.2O.sub.3" resides
in that Bi.sub.2O.sub.3 is not added positively as a glass
component, but contamination with Bi.sub.2O.sub.3 as an impurity is
allowable. Specifically, the phrase means that the content of
Bi.sub.2O.sub.3 is less than 500 ppm (by mass).
[0061] The tempered glass sheet according to this embodiment has a
spectral transmittance in terms of a thickness of 1.0 mm at a
wavelength of 400 to 700 nm of 85% or more, preferably 87% or more,
89% or more, particularly preferably 90% or more. With this, the
color of the tempered glass sheet is faded. Hence, when the
tempered glass sheet is used for an exterior component having such
a form that a part or the whole of the end surface of the tempered
glass sheet is exposed to the outside, high-class appearance can be
provided to the exterior component.
[0062] The tempered glass sheet according to this embodiment has a
chromaticity x of 0.3095 to 0.3120, preferably 0.3096 to 0.3115,
0.3097 to 0.3110, 0.3098 to 0.3107, particularly preferably 0.3100
to 0.3107 in xy chromaticity coordinates (illuminant C, in terms of
a thickness of 1 mm). With this, the color of the tempered glass
sheet is faded. Hence, when the tempered glass sheet is used for an
exterior component having such a form that a part or the whole of
the end surface of the tempered glass sheet is exposed to the
outside, high-class appearance can be provided to the exterior
component.
[0063] The tempered glass sheet according to this embodiment has a
chromaticity y of 0.3160 to 0.3180, preferably 0.3160 to 0.3175,
0.3160 to 0.3170, particularly preferably 0.3160 to 0.3167 in xy
chromaticity coordinates (illuminant C, in terms of a thickness of
1 mm). With this, the color of the tempered glass sheet is faded.
Hence, when the tempered glass sheet is used for an exterior
component having such a form that a part or the whole of the end
surface of the tempered glass sheet is exposed to the outside,
high-class appearance can be provided to the exterior
component.
[0064] In the tempered glass sheet according to this embodiment,
the compression stress value of the compression stress layer is
preferably 300 MPa or more, 500 MPa or more, 600 MPa or more, 700
MPa or more, particularly preferably 800 MPa or more. As the
compression stress value becomes larger, the mechanical strength of
the tempered glass sheet becomes higher. On the other hand, when an
extremely large compression stress is formed on the surface of the
tempered glass sheet, micro cracks are generated on the surface,
which may reduce the mechanical strength of the tempered glass
sheet to the worse. Further, a tensile stress inherent in the
tempered glass sheet may increase extremely. Thus, the compression
stress value of the compression stress layer is preferably 1,500
MPa or less. Note that there is a tendency that the compression
stress value is increased by increasing the content of
Al.sub.2O.sub.3, TiO.sub.2, ZrO.sub.2, MgO, or ZnO in the glass
composition or by reducing the content of SrO or BaO in the glass
composition. Further, there is a tendency that the compression
stress value is increased by shortening the ion exchange time or by
reducing the temperature of an ion exchange solution.
[0065] The depth of the compression stress layer is preferably 10
.mu.m or more, 25 .mu.m or more, 40 .mu.m or more, particularly
preferably 45 .mu.m or more. As the depth of the compression stress
layer becomes larger, the tempered glass sheet is more hardly
cracked even when the tempered glass sheet has a deep flaw, and a
variation in the mechanical strength becomes smaller. On the other
hand, as the depth of the compression stress layer becomes larger,
it becomes more difficult to cut the tempered glass sheet. Thus,
the depth of the compression stress layer is preferably 500 .mu.m
or less, 200 .mu.m or less, 150 .mu.m or less, particularly
preferably 90 .mu.m or less. Note that there is a tendency that the
depth of the compression stress layer is increased by increasing
the content of K.sub.2O or P.sub.2O.sub.5 in the glass composition
or by reducing the content of SrO or BaO in the glass composition.
Further, there is a tendency that the depth of the compression
stress layer is increased by lengthening the ion exchange time or
by increasing the temperature of an ion exchange solution.
[0066] In the tempered glass sheet according to this embodiment, a
part or the whole of the end edge regions at which a cut surface of
the tempered glass sheet and a surface thereof cross to each other
is preferably subjected to chamfering processing, and a part or the
whole of the end edge region at least on the viewer side is
preferably subjected to chamfering processing. Note that only the
end edge region on the device side or both the end edge regions on
the viewer side and the device side may be subjected to chamfering
processing. The chamfering processing is preferably R chamfering.
In this case, R chamfering with a curvature radius of 0.05 to 0.5
mm is preferred. Further, C chamfering with a cut length of 0.05 to
0.5 mm on each side or one side is also suitable. In addition, the
chamfered surface has a surface roughness Ra of preferably 1 nm or
less, 0.7 nm or less, 0.5 nm or less, particularly preferably 0.3
nm or less. With this, cracks originated from end edge regions are
easily prevented, and from the viewpoint of appearance, the
tempered glass sheet can be suitably used for an exterior component
having such a form that a part or the whole of the end surface of
the tempered glass sheet is exposed to the outside. Herein, the
term "surface roughness Ra" refers to a value obtained by
measurement using a method in accordance with JIS B0601: 2001.
[0067] The tempered glass sheet according to this embodiment has a
.beta.-OH value of preferably 0.4 mm.sup.-1 or less, 0.3 mm.sup.-1
or less, 0.28 mm.sup.-1 or less, 0.25 mm.sup.-1 or less,
particularly preferably 0.22 mm.sup.-1 or less. A tempered glass
sheet having a smaller .beta.-OH value has more improved ion
exchange performance.
[0068] The .beta.-OH value of a tempered glass sheet is increased
by (1) selecting a raw material having a high content of water
(such as a hydroxide raw material), (2) adding water into a raw
material, (3) reducing the addition amount of a component capable
of decreasing the amount of water (such as Cl or SO.sub.3) or not
using the component, (4) adopting oxygen combustion or directly
introducing water vapor into a melting furnace at the time of
melting glass, thereby increasing the amount of water in the
atmosphere inside the furnace, (5) performing water vapor bubbling
in molten glass, (6) adopting a large melting furnace, or (7)
reducing the flow rate of molten glass. Thus, the .beta.-OH value
can be reduced by performing the reverse operation of each of the
above-mentioned operations (1) to (7). That is, the .beta.-OH value
is reduced by (8) selecting a raw material having a low content of
water, (9) not adding water into a raw material, (10) increasing
the addition amount of a component capable of decreasing the amount
of water (such as Cl or SO.sub.3), (11) reducing the amount of
water in the atmosphere inside a furnace, (12) performing N.sub.2
bubbling in molten glass, (13) adopting a small melting furnace, or
(14) increasing the flow rate of molten glass.
[0069] The tempered glass sheet according to this embodiment has a
thickness of preferably 3.0 mm or less, 2.0 mm or less, 1.5 mm or
less, 1.3 mm or less, 1.1 mm or less, 1.0 mm or less, 0.8 mm or
less, particularly preferably 0.7 mm or less. On the other hand,
when the thickness is too small, it is difficult to obtain a
desired mechanical strength. Thus, the thickness is preferably 0.1
mm or more, 0.2 mm or more, 0.3 mm or more, 0.4 mm or more,
particularly preferably 0.5 mm or more.
[0070] The tempered glass sheet according to this embodiment has a
density of preferably 2.6 g/cm or less, particularly preferably
2.55 g/cm.sup.3 or less. As the density becomes smaller, the weight
of the tempered glass sheet can be reduced more. Note that the
density is easily decreased by increasing the content of SiO.sub.2,
B.sub.2O.sub.3, or P.sub.2O.sub.5 in the glass composition or by
reducing the content of an alkali metal oxide, an alkaline earth
metal oxide, ZnO, ZrO.sub.2, or TiO.sub.2 in the glass
composition.
[0071] The tempered glass sheet according to this embodiment has a
thermal expansion coefficient in the temperature range of 30 to
380.degree. C. of preferably 80 to 120.times.10.sup.-7/.degree. C.,
85 to 110.times.10.sup.-7/.degree. C., 90 to
110.times.10.sup.-7/.degree. C., particularly preferably 90 to
105.times.10.sup.-7/.degree. C. When the thermal expansion
coefficient is controlled within the above-mentioned ranges, it is
easy to match the thermal expansion coefficient with those of
members made of a metal, an organic adhesive, and the like, and the
members made of a metal, an organic adhesive, and the like are
easily prevented from being peeled off. Note that the thermal
expansion coefficient is easily increased by increasing the content
of an alkali metal oxide or an alkaline earth metal oxide in the
glass composition, and in contrast, the thermal expansion
coefficient is easily decreased by reducing the content of the
alkali metal oxide or the alkaline earth metal oxide.
[0072] The tempered glass sheet according to this embodiment has a
strain point of preferably 500.degree. C. or more, 520.degree. C.
or more, particularly preferably 530.degree. C. or more. As the
strain point becomes higher, the heat resistance is improved more,
and the disappearance of the compression stress layer more hardly
occurs when the tempered glass sheet is subjected to thermal
treatment. Further, as the strain point becomes higher, stress
relaxation more hardly occurs during ion exchange treatment, and
thus the compression stress value can be maintained more easily.
Note that the strain point is easily increased by increasing the
content of an alkaline earth metal oxide, Al.sub.2O.sub.3,
ZrO.sub.2, or P.sub.2O.sub.5 in the glass composition or by
reducing the content of an alkali metal oxide in the glass
composition.
[0073] The tempered glass sheet according to this embodiment has a
temperature at 10.sup.4.0 dPas of preferably 1,280.degree. C. or
less, 1,230.degree. C. or less, 1,200.degree. C. or less,
1,180.degree. C. or less, particularly preferably 1,160.degree. C.
or less. As the temperature at 10.sup.4.0 dPas becomes lower, a
burden on a forming facility is reduced more, the forming facility
has a longer life, and consequently, the production cost of the
tempered glass sheet is more likely to be reduced. The temperature
at 10.sup.4.0 dPas is easily decreased by increasing the content of
an alkali metal oxide, an alkaline earth metal oxide, ZnO,
B.sub.2O.sub.3, or TiO.sub.2 or by reducing the content of
SiO.sub.2 or Al.sub.2O.sub.3.
[0074] The tempered glass sheet according to this embodiment has a
temperature at 10.sup.2.5 dPas of preferably 1,620.degree. C. or
less, 1,550.degree. C. or less, 1,530.degree. C. or less,
1,500.degree. C. or less, particularly preferably 1,450.degree. C.
or less. As the temperature at 10.sup.2.5 dPas becomes lower,
melting at lower temperature can be carried out, and hence a burden
on a glass production facility such as a melting furnace is reduced
more, and the bubble quality of glass is improved more easily. That
is, as the temperature at 10.sup.2.5 dPas becomes lower, the
production cost of the tempered glass sheet is more likely to be
reduced. Note that the temperature at 10.sup.2.5 dPas corresponds
to a melting temperature. Further, the temperature at 10.sup.2.5
dPas is easily decreased by increasing the content of an alkali
metal oxide, an alkaline earth metal oxide, ZnO, B.sub.2O.sub.3, or
TiO.sub.2 in the glass composition or by reducing the content of
SiO.sub.2 or Al.sub.2O.sub.3 in the glass composition.
[0075] The tempered glass sheet according to this embodiment has a
liquidus temperature of preferably 1,100.degree. C. or less,
1,050.degree. C. or less, 1,000.degree. C. or less, 950.degree. C.
or less, 900.degree. C. or less, particularly preferably
880.degree. C. or less. Note that, as the liquidus temperature
becomes lower, the devitrification resistance and formability are
improved more. Further, the liquidus temperature is easily
decreased by increasing the content of Na.sub.2O, K.sub.2O, or
B.sub.2O.sub.3 in the glass composition or by reducing the content
of Al.sub.2O.sub.3, Li.sub.2O, MgO, ZnO, TiO.sub.2, or ZrO.sub.2 in
the glass composition.
[0076] The tempered glass sheet according to this embodiment has a
liquidus viscosity of preferably 10.sup.4.0 dPas or more,
10.sup.4.4 dPas or more, 10.sup.4.8 dPas or more, 10.sup.5.0 dPas
or more, 10.sup.5.4 dPas or more, 10.sup.5.6 dPas or more,
10.sup.6.0 dPas or more, 10.sup.6.2 dPas or more, particularly
preferably 10.sup.6.3 dPas or more. Note that, as the liquidus
viscosity becomes higher, the devitrification resistance and
formability are improved more. Further, the liquidus viscosity is
easily increased by increasing the content of Na.sub.2O or K.sub.2O
in the glass composition or by reducing the content of
Al.sub.2O.sub.3, Li.sub.2O, MgO, ZnO, TiO.sub.2, or ZrO.sub.2 in
the glass composition.
[0077] In the tempered glass sheet according to this embodiment,
suitable tempered glass sheets can be specified by appropriately
selecting suitable content ranges of each component and suitable
amounts of water. Of those, the following tempered glass sheets are
particularly suitable:
(1) a tempered glass sheet comprising, as a glass composition
expressed in mass % in terms of oxides, 50 to 70% of SiO.sub.2, 7
to 20% of Al.sub.2O.sub.3, 0 to 3% of B.sub.2O.sub.3, 10 to 18% of
Na.sub.2O, 2 to 8% of K.sub.2O, 50 to 1,000 ppm of Fe.sub.2O.sub.3,
0 to 50,000 ppm of TiO.sub.2, and 80 to 9,000 ppm of
SnO.sub.2+SO.sub.3+Cl, and having a .beta.-OH value of 0.5
mm.sup.-1 or less; (2) a tempered glass sheet comprising, as a
glass composition expressed in mass % in terms of oxides, 50 to 70%
of SiO.sub.2, 8 to 20% of Al.sub.2O.sub.3, 0 to 2% of
B.sub.2O.sub.3, 11 to 18% of Na.sub.2O, 2 to 7% of K.sub.2O, 80 to
500 ppm of Fe.sub.2O.sub.3, 0 to 30,000 ppm of TiO.sub.2, and 100
to 8,000 ppm of SnO.sub.2+SO.sub.3+Cl, and having a .beta.-OH value
of 0.4 mm.sup.-1 or less; (3) a tempered glass sheet comprising, as
a glass composition expressed in mass % in terms of oxides, 50 to
70% of SiO.sub.2, 10 to 18% of Al.sub.2O.sub.3, 0 to 1.5% of
B.sub.2O.sub.3, 12 to 17% of Na.sub.2O, 3 to 7% of K.sub.2O, 100 to
300 ppm of Fe.sub.2O.sub.3, 0 to 10,000 ppm of TiO.sub.2, and 300
to 7,000 ppm of SnO.sub.2+SO.sub.3+Cl, and having a .beta.-OH value
of 0.4 mm.sup.-1 or less; and (4) a tempered glass sheet
comprising, as a glass composition expressed in mass % in terms of
oxides, 50 to 70% of SiO.sub.2, 12 to 18% of Al.sub.2O.sub.3, 0 to
1% of B.sub.2O.sub.3, 12 to 16% of Na.sub.2O, 3 to 7% of K.sub.2O,
100 to 300 ppm of Fe.sub.2O.sub.3, 0 to 5,000 ppm of TiO.sub.2, and
300 to 3,000 ppm of SnO.sub.2+SO.sub.3+Cl, and having a .beta.-OH
value of 0.3 mm.sup.-1 or less.
[0078] A glass sheet to be tempered according to an embodiment of
the present invention comprises, as a glass composition expressed
in mass % in terms of oxides, 50 to 70% of SiO.sub.2, 5 to 20% of
Al.sub.2O.sub.3, 0 to 5% of B.sub.2O.sub.3, 8 to 18% of Na.sub.2O,
2 to 9% of K.sub.2O, and 30 to 1,500 ppm of Fe.sub.2O.sub.3, and
having a spectral transmittance in terms of a thickness of 1.0 mm
at a wavelength of 400 to 700 nm of 85% or more, a chromaticity x
of 0.3100 to 0.3120 in xy chromaticity coordinates (illuminant C,
in terms of a thickness of 1 mm), and a chromaticity y of 0.3160 to
0.3180 in xy chromaticity coordinates (illuminant C, in terms of a
thickness of 1 mm). The technical features of the glass sheet to be
tempered according to this embodiment are the same as the technical
features of the tempered glass sheet according to this embodiment
described previously. Herein, the description thereof is omitted
for convenience sake.
[0079] When the glass sheet to be tempered according to this
embodiment is subjected to ion exchange treatment in a KNO.sub.3
molten salt at 430.degree. C., it is preferred that the compression
stress value of the compression stress layer in the surface be 300
MPa or more and the depth of the compression stress layer be 10
.mu.m or more, it is more preferred that the compression stress
value of the compression stress layer be 600 MPa or more and the
depth of the compression stress layer be 40 .mu.m or more, and it
is particularly preferred that the compression stress value of the
compression stress layer be 800 MPa or more and the depth of the
compression stress layer be 60 .mu.m or more.
[0080] When ion exchange treatment is performed, the temperature of
the KNO.sub.3 molten salt is preferably 400 to 550.degree. C., and
the ion exchange time is preferably 2 to 10 hours, particularly
preferably 4 to 8 hours. With this, the compression stress layer
can be properly formed easily. Note that the glass sheet to be
tempered according to this embodiment has the above-mentioned glass
composition, and hence the compression stress value and depth of
the compression stress layer can be increased without using a
mixture of a KNO.sub.3 molten salt and an NaNO.sub.3 molten salt or
the like.
[0081] The glass sheet to be tempered and tempered glass sheet
according to this embodiment can be produced as described
below.
[0082] A glass sheet can be produced by first placing glass raw
materials, which have been blended so as to have the
above-mentioned glass composition, in a continuous melting furnace,
melting the glass raw materials by heating at 1,500 to
1,600.degree. C., fining the molten glass, and feeding the
resultant to a forming apparatus, followed by forming into a sheet
shape or the like and annealing.
[0083] It is preferred to adopt an overflow down-draw method as a
method of forming glass into a sheet shape. The overflow down-draw
method is a method by which glass sheets can be massively produced
at low cost and by which a large glass sheet can be easily
produced.
[0084] Various forming methods other than the overflow down-draw
method may also be adopted. For example, forming methods may be
adopted, such as a float method, a down-draw method (such as a slot
down method or a re-draw method), a roll-out method, and a press
method.
[0085] Next, the resultant glass sheet is subjected to tempering
treatment, thereby being able to produce a tempered glass sheet.
The glass sheet may be cut into pieces having a predetermined size
before the tempering treatment, but the cutting after the tempering
treatment is advantageous in terms of cost.
[0086] The tempering treatment is preferably ion exchange
treatment. Conditions for the ion exchange treatment are not
particularly limited, and optimum conditions may be selected in
view of, for example, the viscosity properties, applications,
thickness, and inner tensile stress of a glass sheet. The ion
exchange treatment can be performed, for example, by immersing a
glass sheet in a KNO.sub.3 molten salt at 400 to 550.degree. C. for
1 to 8 hours. Particularly when the ion exchange of K ions in the
KNO.sub.3 molten salt with Na components in the glass sheet is
performed, it is possible to form efficiently a compression stress
layer in a surface of the glass sheet.
Example 1
[0087] Examples of the present invention are hereinafter described.
Note that the following examples are merely illustrative. The
present invention is by no means limited to the following
examples.
[0088] Tables 1 to 3 show Examples of the present invention (Sample
Nos. 1 to 16).
TABLE-US-00001 TABLE 1 Example No. 1 No. 2 No. 3 No. 4 No. 5 No. 6
wt % SiO.sub.2 57.4 57.3 56.5 58.5 57.2 58.2 Al.sub.2O.sub.3 12.9
13.0 13.0 13.3 13.0 14.0 B.sub.2O.sub.3 2.0 2.0 2.0 -- -- --
Li.sub.2O -- 0.1 1.0 0.1 0.1 0.1 Na.sub.2O 14.5 14.5 14.5 14.8 14.5
13.5 K.sub.2O 5.0 5.0 5.0 5.1 7.0 6.5 M.sub.gO 2.0 2.0 2.0 2.0 2.0
2.0 C.sub.aO 2.0 2.0 2.0 2.0 2.0 2.0 Z.sub.rO.sub.2 4.0 4.0 4.0 4.1
4.0 3.5 ppm Cl -- 500 -- 300 -- 200 SnO.sub.2 2,000 -- -- -- 1,000
1,500 SO.sub.3 -- -- 200 500 300 -- Fe.sub.2O.sub.3 150 160 120 190
140 150 TiO.sub.2 50 40 30 70 60 50 .rho. (g/cm.sup.3) 2.54 2.55
2.56 2.55 2.56 2.52 .alpha. (.times.10.sup.-7/.degree. C.) 99 100
100 101 106 101 Ps (.degree. C.) 530 524 485 533 523 534 Ta
(.degree. C.) 571 565 524 577 566 579 Ts (.degree. C.) 769 765 714
791 777 798 10.sup.4.0 dPa s (.degree. C.) 1,115 1,110 1,052 1,140
1,123 1,156 10.sup.3.0 dPa s (.degree. C.) 1,296 1,289 1,231 1,319
1,300 1,339 10.sup.2.5 dPa s (.degree. C.) 1,411 1,403 1,345 1,432
1,412 1,455 TL (.degree. C.) 880 880 870 880 860 880
log.sub.10.eta.TL (dPa s) 6.0 6.0 5.5 6.3 6.4 6.5 .beta.-OH
(mm.sup.-1) 0.25 0.26 0.22 0.20 0.28 0.22 CS (MPa) 925 910 737 893
822 884 DOL (.mu.m) 37 35 27 42 47 47 Transmittance Wavelength 91
91 91 91 91 91 (%) 400 nm Wavelength 92 92 92 92 92 92 550 nm
Wavelength 92 92 92 92 92 92 700 nm Chromaticity x 0.3105 0.3104
0.3103 0.3105 0.3104 0.3104 Chromaticity y 0.3165 0.3166 0.3164
0.3166 0.3166 0.3166
TABLE-US-00002 TABLE 2 Example No. 7 No. 8 No. 9 No. 10 No. 11 wt %
SiO.sub.2 59.1 58.0 58.1 58.4 57.8 Al.sub.2O.sub.3 12.0 13.6 13.3
13.0 14.0 B.sub.2O.sub.3 -- -- -- -- -- Li.sub.2O 0.1 0.1 0.1 0.1
0.1 Na.sub.2O 13.0 14.8 14.8 14.5 14.5 K.sub.2O 7.0 5.5 5.5 5.5 5.5
M.sub.gO 2.0 2.0 2.0 2.0 2.0 C.sub.aO 2.0 1.4 1.4 2.0 2.0
Z.sub.rO.sub.2 4.5 4.4 4.7 4.5 4.0 ppm Cl -- 100 -- -- -- SnO.sub.2
3,000 1,500 1,000 -- -- SO.sub.3 -- -- -- 300 400 Fe.sub.2O.sub.3
150 210 170 120 110 TiO.sub.2 50 80 30 20 30 .rho. (g/cm.sup.3)
2.54 2.54 2.54 2.55 2.54 .alpha. (.times.10.sup.-7/.degree. C.) 102
103 103 102 102 Ps (.degree. C.) 532 533 534 533 536 Ta (.degree.
C.) 576 579 579 577 580 Ts (.degree. C.) 794 798 799 793 796
10.sup.4.0 dPa s (.degree. C.) 1,149 1,152 1,149 1,142 1,147
10.sup.3.0 dPa s (.degree. C.) 1,330 1,333 1,327 1,319 1,326
10.sup.2.5 dPa s (.degree. C.) 1,445 1,449 1,441 1,431 1,440 TL
(.degree. C.) 880 870 880 880 870 log.sub.10.eta.TL (dPa s) 6.4 6.6
6.5 6.4 6.5 .beta.-OH (mm.sup.-1) 0.22 0.25 0.20 0.19 0.19 CS (MPa)
880 880 873 906 921 DOL (.mu.m) 49 49 48 43 44 Transmittance
Wavelength 91 91 91 91 91 (%) 400 nm Wavelength 92 92 92 92 92 550
nm Wavelength 92 92 92 92 92 700 nm Chromaticity x 0.3105 0.3105
0.3105 0.3103 0.3103 Chromaticity y 0.3165 0.3166 0.3165 0.3164
0.3164
TABLE-US-00003 TABLE 3 Example No. 12 No. 13 No. 14 No. 15 No. 16
wt % SiO.sub.2 58.4 58.4 58.4 58.4 58.4 Al.sub.2O.sub.3 13 13 13 13
13 B.sub.2O.sub.3 -- -- -- -- -- Li.sub.2O 0.1 0.1 0.1 0.1 0.1
Na.sub.2O 14.5 14.5 14.5 14.5 14.5 K.sub.2O 5.5 5.5 5.5 5.5 5.5
M.sub.gO 2 2 2 2 2 C.sub.aO 2 2 2 2 2 Z.sub.rO.sub.2 4.5 4.5 4.5
4.5 4.5 ppm Cl -- -- -- -- -- SnO.sub.2 3,000 3,000 3,000 3,000
3,000 SO.sub.3 -- -- -- -- -- Fe.sub.2O.sub.3 230 230 230 230 230
TiO.sub.2 60 5,000 60 60 60 CeO.sub.2 -- -- 5,000 -- -- WO.sub.3 --
-- -- 5,000 -- NiO -- -- -- -- 50 Transmittance Wavelength 91 91 91
90 91 (%) 400 nm Wavelength 91 91 91 91 90 550 nm Wavelength 90 90
91 90 90 700 nm Chromaticity x 0.3099 0.3100 0.3102 0.3101 0.3103
Chromaticity y 0.3163 0.3165 0.3164 0.3165 0.3166
[0089] Table 4 shows the raw material composition of Sample Nos. 12
to 16.
TABLE-US-00004 TABLE 4 Silicon oxide Aluminum oxide Sodium
carbonate Potassium carbonate Lithium carbonate Magnesium oxide
Calcium carbonate Zirconium silicate Tin oxide Titanium oxide
Cerium oxide Tungsten oxide Nickel oxide
[0090] Each of the samples in the tables was produced as described
below. First, glass raw materials were blended so as to have glass
compositions shown in the tables, and melted at 1,580.degree. C.
for 8 hours using a platinum pot. Thereafter, the resultant molten
glass was cast on a carbon plate and formed into a sheet shape. The
resultant glass sheet was evaluated for its various properties.
[0091] The density .rho. is a value obtained by measurement using a
well-known Archimedes method.
[0092] The thermal expansion coefficient .alpha. is a value
obtained by measurement of an average thermal expansion coefficient
in the temperature range of 30 to 380.degree. C. using a
dilatometer.
[0093] The strain point Ps and the annealing point Ta are values
obtained by measurement based on a method of ASTM C336.
[0094] The softening point Ts is a value obtained by measurement
based on a method of ASTM C338.
[0095] The temperatures at viscosities at high temperature of
10.sup.4.0 dPas, 10.sup.3.0 dPas, and 10.sup.2.5 dPas are values
obtained by measurement using a platinum sphere pull up method.
[0096] The liquidus temperature TL is a value obtained by
measurement of a temperature at which crystals of glass deposit
after glass powder that has passed through a standard 30-mesh sieve
(sieve opening: 500 .mu.m) and remained on a 50-mesh sieve (sieve
opening: 300 .mu.m) is placed in a platinum boat and then kept in a
gradient heating furnace for 24 hours.
[0097] The liquidus viscosity log.sub.10.eta..sub.TL is a value
obtained by measurement of the viscosity of glass at the liquidus
temperature using a platinum sphere pull up method.
[0098] As evident from Tables 1, 2, and 3, each of Sample Nos. 1 to
16 having a density of 2.56 g/cm.sup.3 or less and a thermal
expansion coefficient of 99 to 106.times.10.sup.-7/.degree. C. was
found to be suitable for a material for a tempered glass sheet,
i.e., a glass sheet to be tempered.
[0099] Further, each of the samples has a liquidus viscosity of
10.sup.5.5 dPas or more, and hence is satisfactory in formability.
In addition, each of the samples has a temperature at 10.sup.4.0
dPas of 1,156.degree. C. or less, and hence reduces a burden on a
forming facility. Moreover, each of the samples has a temperature
at 10.sup.2.5 dPas of 1,455.degree. C. or less, and hence is
expected to allow a large number of glass sheets to be produced at
low cost with high productivity. Note that the glass compositions
of a surface layer of a glass sheet before and after ion exchange
treatment are different from each other microscopically, but the
glass composition of the whole glass does not substantially change
before and after the ion exchange treatment.
[0100] Subsequently, both surfaces of each of the samples were
subjected to optical polishing, and then subjected to ion exchange
treatment through immersion in a KNO.sub.3 molten salt at
440.degree. C. for 6 hours. After the ion exchange treatment, the
surface of each of the samples was washed. Then, the compression
stress value CS and depth DOL of a compression stress layer in the
surface were calculated from the number of interference stripes and
each interval between the interference fringes, the interference
fringes being observed with a surface stress meter (FSM-6000
manufactured by Toshiba Corporation). In the calculation, the
refractive index and optical elastic constant of each of the
samples were set to 1.52 and 28 [(nm/cm)/MPa], respectively.
[0101] As evident from Tables 1 to 3, when each of Sample Nos. 1 to
16 was subjected to ion exchange treatment using the KNO.sub.3
molten salt, the CS and DOL of each of the samples were found to be
737 MPa or more and 27 .mu.m or more, respectively.
[0102] The transmittance of a tempered glass sheet (1 mm) whose
both surfaces had been subjected to mirror polishing was measured
by FT-IR. After that, the .beta.-OH value thereof was calculated by
using the following equation.
.beta.-OH value=(1/X)log.sub.10(T.sub.1/T.sub.2)
[0103] X: thickness (mm)
[0104] T.sub.1: transmittance (%) at a reference wavelength of
3,846 cm.sup.-1
[0105] T.sub.2: minimum transmittance (%) at a hydroxyl group
absorption wavelength of around 3,600 cm.sup.-1
[0106] Both surfaces of each of the samples were subjected to
mirror polishing so that each of the samples had a thickness of 1.0
mm. Then, the spectral transmittance thereof was measured at a
wavelength of 400 to 700 nm. UV-3100 PC (manufactured by Shimadzu
Corporation) was used as a measurement apparatus and the
measurement was performed at a slit width of 2.0 nm at a medium
scan speed at a sampling pitch of 0.5 nm. Further, the same
apparatus was used to evaluate the chromaticity of each of the
samples. Note that illuminant C was used as an illuminant.
[0107] As evident from Tables 1 to 3, each of Sample Nos. 1 to 16
had a spectral transmittance at a wavelength of 400 to 700 nm of
90% or more, and had x and y in xy chromaticity coordinates of
0.3099 to 0.3105 and 0.3163 to 0.3166, respectively.
Example 2
[0108] Glass raw materials were blended so that the glass
composition shown in No. 10 of Table 2 was achieved. After that,
the blended glass materials were formed into glass sheets by an
overflow down-draw method so that the glass sheets have a thickness
of 1.0 mm, 0.7 mm, and 1.1 mm, respectively. Thus, glass sheets to
be tempered were produced. Subsequently, R chamfering processing
with a curvature radius of 0.1 mm was applied to the whole of the
end edge regions on the viewer side and the device side in the
resultant glass sheet to be tempered (having a thickness of 1.0
mm). Further, R chamfering processing with a curvature radius of
0.25 mm was applied to the whole of the end edge regions on the
viewer side and the device side in the resultant glass sheet to be
tempered (having a thickness of 0.7 mm). Besides, R chamfering
processing with a curvature radius of 0.3 mm was applied to the
whole of the end edge region on the viewer side in the resultant
glass sheet to be tempered (having a thickness of 1.1 mm). For
reference, FIG. 1 illustrates a schematic cross-sectional view of a
glass sheet to be tempered in its thickness direction in the case
where R chamfering processing has been applied to the end edge
regions of the glass sheet to be tempered as described above.
INDUSTRIAL APPLICABILITY
[0109] The tempered glass sheet of the present invention is
suitable for a cover glass of a cellular phone, a digital camera, a
PDA, or the like, or a glass substrate for a touch panel display or
the like. Further, the tempered glass sheet of the present
invention can be expected to find use in applications requiring a
high mechanical strength, for example, window glass, a substrate
for a magnetic disk, a substrate for a flat panel display, a cover
glass for a solar cell, a cover glass for a solid-state image
sensing device, and tableware, in addition to the above-mentioned
applications.
* * * * *